The disclosure relates generally to fiber optic connectors and more particularly to a fiber optic connector that reduces or eliminates the formation of air voids within adhesive used in the fiber optic connector. Related components, cable assemblies, and methods are also disclosed.
In a system that uses fiber optic cables, there are typically many locations where the cables connect to equipment or other fiber optic cables. Fiber optic connectors are provided on the ends of the cables to allow the transfer of light at these connection points. A fiber optic connector typically includes a ferrule with one or more bores that receive optical fiber(s) from the cable. The ferrule is held by a ferrule holder and serves to align the optical fiber(s) from the cable with optical fiber(s) or waveguides in a mating component (e.g., another connector or equipment).
The process of terminating individual optical fibers from a cable is referred to as “connectorization.” Connectorization is an important step in the installation of fiber optic systems, whether done in a factory or the field. This is partly due to the number of potential sources for damage during the connectorization process. For example, one or more layers of material are typically stripped from the glass portion of the optical fiber so that only the glass portion (i.e., core and cladding) is inserted into the ferrule of the connector. In many instances this includes stripping a 900 micron-diameter buffer layer in a first step, and then stripping a 250 micron-diameter acrylic coating in a second step so that only a 125 micron-diameter glass portion remains. Stripping tools have been developed to reduce the likelihood of damaging the glass portion during these steps, but the potential remains nonetheless, especially in the region where a stripping tool begins to remove the buffer layer and/or outer coating.
Even if an optical fiber is properly stripped and prepared for insertion into the bore (“micro-hole”) of a ferrule, the insertion itself can be challenging and has the potential to introduce flaws in the glass portion. For example, the ferrule bore typically includes a cone-shaped lead-in to facilitate directing the glass portion into the bore. An adhesive such as epoxy is first injected into the bore from the back end of the ferrule holder, thereby filling the bore, lead-in, and any space within the ferrule holder between the rear end of the ferrule and the injection needle. The injection needle is then removed, and the optical fiber is inserted through the adhesive and into the bore of the ferrule. Shear forces between the fiber and the adhesive may cause the fiber to buckle within the lead-in of the ferrule bore and perhaps even make contact with the edge of the ferrule.
An optical fiber that sustains damage from either or both of the above-described scenarios may still withstand failure in most conditions, especially if the glass portion is properly supported by adhesive within the ferrule. However, sometimes air or other gas can get trapped within the adhesive and cause voids. These voids may even end up around the damaged region of the glass portion and increase the potential for a fiber break. This is particularly true for cables used in an outside plant environment (i.e., outdoor cables or indoor/outdoor cables), which may be exposed to a variety of environmental and mechanical extremes.
These aspects can be better understood with reference to FIG. 3, which shows a portion of a conventional fiber optic connector 10 in an assembled state. A ferrule 12 is received in a ferrule holder 14, and an optical fiber 16 is secured in a ferrule bore 18 by adhesive 20. As can be seen, a buffer layer 22 and outer coating 24 have been stripped from the optical fiber 16 so that only a glass portion 26 (core and cladding) are inserted into the ferrule bore 18. The adhesive may surround portions of the outer coating 24 and buffer layer 22 as well.
An air void or bubble 30 may form in the adhesive when the adhesive is injected and/or when the adhesive injection needle (not shown) is withdrawn. Even if the air void 30 is formed in a region of the adhesive remote from where the optical fiber 16 is inserted, the air void 30 may migrate toward the optical fiber 16 during or after the insertion. This may ultimately result in the air void 30 contacting or surrounding a region of the glass portion 26 that is prone to damage. As can be seen, the damaged regions mentioned in both of the above-describe scenarios may be the same. That is, where the outer coating 24 is stripped from the optical fiber 16 may be the same place where the fiber has increased potential to buckle and contact an edge of the ferrule 12 during insertion into the ferrule bore 18. The presence of an air void creates a non-uniform distribution of the adhesive 20 around this damage-prone region in the lead-in 32 of the ferrule bore 18, which in turn can lead to increased loads/stresses on the damage-prone region during thermal expansions and the like. The loads/stresses may result in the optical fiber 16 breaking in this region. Therefore, a need exists to address the above-mentioned challenges.